1. Field of the Invention
The present invention relates to a display panel, and more particularly to an apparatus and method for forming phosphor layers between barrier ribs on a display panel.
2. Description of the Related Art
As generally known in the art, a flat panel display (FPD) refers to a liquid crystal display (LCD) or a plasma display panel (PDP). Especially, a plasma display panel is a flat display panel including a pair of substrates (usually glasses) as base members, which are opposed to and apart from each other so as to form an electric discharge space between them. The plasma display panel has ultraviolet ray-excited phosphor layers formed in the discharge space, so that the phosphor layers can be excited by electric discharge, thereby displaying colors. Usually, a display panel has phosphor layer of R (red), G (green), and B (blue).
In order to form phosphor layers on a display panel as described above, phosphor powder having particle sizes of several μm to several tens of μm is used. Such phosphors are applied on the display panel by a slurry method, a screen printing method, an inkjet printing method, etc.
Specifically, in the slurry method, base coating solution is applied and dried on an upper surface of a lower panel on which barrier ribs have been formed, and slurry containing phosphors, surfactants, dispersants, etc., is then applied on a central portion of the lower panel. Then, the lower panel is rotated so that the slurry can be uniformly distributed. Thereafter, a shadow mask is place above the lower panel, and ultraviolet rays are then shed on the lower panel through the shadow mask. Thereafter, the lower panel is subjected to a development process, in which the lower panel is washed by warm water, so that phosphor layers patterns of specific colors are formed on the panel.
Next, in the screen printing method, a paste containing phosphors is squeezed and transcribed onto a screen such as a silk screen or a stainless mesh by a squeezer, so that phosphor layer patterns of specific colors are formed on the panel.
Of course, in order to facilitate separation of the screen from the panel, the panel and the screen should be apart from each other with a sufficient gap between them. Further, a stable squeeze angle is set for rotation of the paste, and a relatively low squeeze pressure should be maintained in order to prevent the screen from being damaged. Further, a squeeze velocity should be set in consideration of fluidity of the paste.
Meanwhile, in the inkjet printing method, ink containing phosphors is sprayed directly into gaps between barrier ribs on the panel, so that phosphor layer patterns of specific colors are formed on the panel.
However, the related art methods of forming phosphor layers, as described above, have the following problems.
The related art slurry method for forming phosphor layers on a panel has many steps, which is expansive and requires a large space for manufacturing facilities. Also, a large quantity of pure water is required by the method. Further, in the related art slurry method, injection, development, and dehydration of phosphors require consumption of a large quantity of electric energy, which further increases the manufacturing cost.
Meanwhile, in the related art screen printing method for forming phosphor layers on a panel, it is difficult for some workers to form phosphor layer patterns with a specific size and shape. Further, the screen may be blocked, causing it to be difficult to form phosphor layers with a high resolution. Moreover, mechanical processing is necessary in order to wash used masks, thereby causing the manufacturing process to be more complicated.
Also, in the related art inkjet printing method for forming phosphor layers on a panel, when a phosphor layer pattern is not linear, scanning of the phosphor layer pattern is necessary, requiring a long time, which deteriorates productivity. Meanwhile, when a plurality of nozzle heads and CCD (charge coupled device) cameras are employed in order to improve the productivity, a large space and a complicated construction for installation of them are necessary.